The invention relates to a system for the relative angle-of-rotation adjustment of a camshaft of an internal-combustion engine with respect to a driving wheel having an adjusting unit which has an interior part non-rotatably connected with the camshaft, the adjusting unit having a cell wheel which encloses the interior part and which has several cells distributed along the circumference and bounded by webs, which cells are divided by webs or blades of the interior part angularly movably guided therein into two pressure spaces respectively, during whose hydraulic pressure admission or pressure relief, the camshaft can be rotated by way of the webs or blades between two end positions relative to the cell wheel and that a movable locking element interacts with at least one counterelement in the respective other one of the two componentsxe2x80x94cell wheel or interior part, that the locking element is arranged in a hydraulic line leading to a pressure space and, only in an unlocked position, opens up the hydraulic line to the pressure space, and that bores leading to the pressure spaces are arranged in the interior part, the openings of the bores in the locked end position of the adjusting unit being closed off by the webs of the cell wheel.
From German Patent Document DE 196 23 818 A1, a system of the above-mentioned type is known in which the camshaft adjuster can be locked in an end position by means of a locking element arranged in the rotor of the camshaft adjuster. By way of hydraulic lines leading to the locking element, the locking element can be changed from its locking position into an unlocked position. When the camshaft adjuster is unlocked, as a result of the hydraulic adjustment of the rotor relative to the driving wheel of the camshaft, the timing of the inlet and outlet valves respectively can be changed as desired. The system illustrated in German Patent Document DE 196 23 818 A1 is constructed such that the pressure admission to the hydraulic chambers, by means of which the adjustment of the rotor with respect to the stator of the camshaft adjuster takes place, and the hydraulic pressure admission for unlocking the locking pin takes place in parallel. However, this does not always ensure that the locking of the adjusting unit is released first before the rotor is changed into an adjusting position by the pressure chambers or hydraulic chambers constructed in the adjusting unit. As a result, operating conditions may occur in which the adjusting unit does not operate in a reliable manner.
German Patent Document DE 198 25 287 A1 shows a camshaft adjuster in the case of which the pressure oil feeding to the working chambers is controlled by way of the locking element provided in the camshaft adjuster. As a result of the change of the locking element to the unlocked position, the locking element opens up a pressure duct and the working chambers constructed in the camshaft adjuster are isochronously acted upon by pressure oil by way of ducts leading to the chambers.
It is therefore an object of the invention to improve a system of the above-mentioned type such that starting noises during the activation of the camshaft adjuster are prevented or reduced and the useful life or the functionality of the locking unit is increased.
According to the invention, this object is achieved by providing a system having an adjusting unit which has an interior part non-rotatably connected with the camshaft, the adjusting unit having a cell wheel which encloses the interior part and which has several cells distributed along the circumference and bounded by webs, which cells are divided by webs or blades of the interior part angularly movably guided therein into two pressure spaces respectively, during whose hydraulic pressure admission or pressure relief, the camshaft can be rotated by way of the webs or blades between two end positions relative to the cell wheel and that a movable locking element interacts with at least one counterelement in the respective other one of the two componentsxe2x80x94cell wheel or interior part, that the locking element is arranged in a hydraulic line leading to a pressure space and, only in an unlocked position, opens up the hydraulic line to the pressure space, and that bores leading to the pressure spaces are arranged in the interior part, the openings of the bores in the locked end position of the adjusting unit being closed off by the webs of the cell wheel, characterized in that the locking element can be changed into a first unlocking position, in which the bore in the web controlled by the locking element as well as the bores in the interior part leading to the pressure spaces are still closed, and in that the locking element can be changed into a second unlocking position in which first the bore leading to the pressure space is opened up by the-locking element and, after an initial adjusting path (xcex1) of the interior part, also the bores leading to the pressure spaces are opened up.
In contrast to the locking unit of a camshaft adjuster illustrated in German Patent Document DE 198 25 287 A1, the locking element is advantageously by means of a first adjusting lift first changed into an unlocked position in which, however, the hydraulic duct controlled by the locking element as well as the oil feeding bores leading to the other pressure spaces are still closed. However, when the locking element is lifted beyond its unlocked position, the hydraulic duct leading to the pressure space of the adjusting unit is opened up before, after a short initial adjusting path of the rotor of the adjusting unit, the oil feeding bores leading to the remaining pressure spaces are also opened up and the rotor can be further adjusted in a desirable manner with respect to the stator of the adjusting unit. As a result of this type of pressure admission, a starting rattle of the camshaft adjuster is prevented or reduced. Furthermore, the bearing of the locking element in the locking bore can be reduced. This considerably improves the useful life and the functionality of the locking device.
Additional advantages and advantageous further developments of the invention are contained in the subclaims and the description.
The locking element is received in a bore which is arranged in a web or a blade of the rotor. The bore is arranged in a hydraulic-oil feed line which leads to a pressure space arranged in the adjusting unit. When the locking element is in a locked position, the hydraulic line is closed by the locking element. In an unlocked position, the locking element opens up the hydraulic line to the pressure space.